Looking to the skies in Kiribati—La Niña and rainfall variability in the Central Pacific

Rainfall is essential to recharge the freshwater lens that lies beneath coral atolls in Kiribati. Without it, the i-Kiribati people would not be able to grow plants and crops vital to their livelihood.

Freshwater can be extremely scarce in the Republic of Kiribati, home to over 100,000 people scattered across 22 islands in the Central Pacific. Each year after a long dry season, significant rainfall is generally expected to arrive during November or December. Yet over the last few months only a tiny amount of rain has fallen. The islands are dry.

This is consistent with forecasts that predict La Niña conditions will result in below normal rainfall during the 2010-11 wet season across the Gilbert Islands of Kiribati.

"We are likely to see drought conditions for most of the Gilbert Group. In the last La Niña in 2007-08 there were drought conditions that went on for 15-16 months during that time," Douglas Ramsay, Manager for the Pacific Rim at NIWA, the New Zealand National Institute of Water and Atmospheric Research explains.

This rainfall is essential not only to fill rainwater tanks but also to recharge the freshwater lens that lies beneath these coral atolls. It is this water that is used for the majority of water supply via wells and infiltration galleries. The lens also allows for the growth of breadfruit, coconut palms, giant taro, pandanus and other plants species to support the livelihood of the i-Kiribati people.

In the densely populated capital of South Tarawa, it is estimated that the current demand for safe chlorinated groundwater piped to households is already 40% above the sustainable yield of the utilised lens. Without enough supply, households resort to using the polluted well. As a result, mortality rates for children due to waterborne diseases are in the order of 11 in every 1000 children, amongst the highest in the Pacific.

Under the KAPII (Kiribati Adaptation Program – Pilot Implementation Phase II), 14 outer islands in the Gilbert Group are receiving new rain gauges. KAPII is a project that aims to reduce Kiribati’s vulnerability to climate change, climate variability and sea level rise through adaptation. The islands of Abaiang, Abemama, Aranuka , Kuria, Maiana, Makin, Marakei, North Tarawa, Nikunau, Nonouti, Onotoa, Tabiteuea North, Tabiteuea South, and Tamana will have gauges installed and training provided for the water technician based on each island to record rainfall data in compliance with Kiribati Meteorological Service standards.

Before the installation of the new gauges, a great deal of data was not being collected, and the government lacked information for planning for drought and high intensity rainfall events.

Ueneta Toorua, Research Officer at the Kiribati Meteorological Service explains. "Our islands are small and widely scattered so rainfall varies between them. The general pattern is that the islands north of the equator have higher rainfall than those in the South."

Besides this, it is also the generally hot and dry weather that has shaped customary practices on the islands.

"The temperature in Kiribati is very consistent throughout the year. This is important for drying copra and the production of dried fish. Our traditional ways are helped by having a consistent climate," said Mr. Toorua.

As global temperatures increase due to climate change, it is anticipated that average rainfall volumes and the intensity of extreme rainfall events will increase in Kiribati. Yet this rainfall may vary greatly between the islands or fall away from the islands where it is needed most.

"Across the equatorial belt we are likely to see higher rainfall on average but that will be higher intensity, more extreme rainfall. Whether we see more intense droughts is still something that no one really knows. It will depend on how El Niños and La Niñas change with climate change," Mr. Ramsay said.

Mr. Toorua and his colleagues at the Kiribati Meteorological Service have already seen evidence of this: "Looking at the long term trends there is an increase here in temperature and also in rainfall. On Tarawa we have more data and it has clearly shown that there is a gradual increase in both. However there may be variation in these trends between different islands."

With the installation of rain gauges across the scattered atolls of the Gilbert Group, the hope is that the data collected will make it possible to answer some of these questions that are so fundamental to the future of Kiribati.

The Government of Kiribati KAPII project is supported by the World Bank, the Global Environment Facility, AusAID and NZAID.